Kufunika kwa okosijeni wa Chemical kumatchedwanso chemical oxygen demand (chemical oxygen demand), yotchedwa COD. Ndi kugwiritsa ntchito mankhwala okosijeni (monga potaziyamu permanganate) kuti oxidize ndi kuwola oxidizable zinthu m'madzi (monga organic kanthu, nitrite, ferrous mchere, sulfide, etc.), ndiyeno kuwerengera kumwa mpweya potengera kuchuluka kwa zotsalira. okosijeni. Monga biochemical oxygen demand (BOD), ndi chizindikiro chofunikira cha kuipitsidwa kwa madzi. Gawo la COD ndi ppm kapena mg/L. Mtengo wocheperako, m'pamenenso kuipitsidwa kwamadzi kumapepuka.
Zomwe zimachepetsa m'madzi zimaphatikizapo zinthu zosiyanasiyana, nitrite, sulfide, mchere wa ferrous, etc. Koma chachikulu ndi organic matter. Chifukwa chake, kufunikira kwa okosijeni wamankhwala (COD) nthawi zambiri amagwiritsidwa ntchito ngati chizindikiritso choyezera kuchuluka kwa zinthu zomwe zili m'madzi. Kuchuluka kwa okosijeni komwe kumafunikira, m'pamenenso kuipitsidwa kwa madzi ndi zinthu zamoyo kumachuluka. Kutsimikiza kwa kufunikira kwa okosijeni wamankhwala (COD) kumasiyanasiyana malinga ndi kutsika kwa zinthu mu zitsanzo zamadzi ndi njira yotsimikizira. Njira zomwe zimagwiritsidwa ntchito kwambiri masiku ano ndi njira ya acidic potassium permanganate oxidation ndi njira ya potassium dichromate oxidation. Njira ya potassium permanganate (KMnO4) imakhala ndi mlingo wochepa wa okosijeni, koma ndi wosavuta. Itha kugwiritsidwa ntchito kudziwa kuchuluka kwa zinthu zomwe zili m'madzi amadzimadzi komanso madzi aukhondo komanso madzi apansi panthaka. Njira ya potassium dichromate (K2Cr2O7) imakhala ndi kuchuluka kwa okosijeni komanso kuberekana kwabwino. Ndikoyenera kudziwa kuchuluka kwa zinthu zomwe zili m'madzi mu zitsanzo zamadzi pakuwunika kwamadzi onyansa.
Organic zinthu ndizovulaza kwambiri machitidwe amadzi am'mafakitale. Madzi okhala ndi zinthu zambiri zachilengedwe amawononga utomoni wosinthanitsa ndi ma ion akadutsa munjira yochotsa mchere, makamaka utomoni wosinthanitsa ndi anion, womwe ungachepetse kusinthana kwa utomoni. Organic zinthu zitha kuchepetsedwa pafupifupi 50% pambuyo pretreatment (coagulation, kumveketsa ndi kusefera), koma sangathe kuchotsedwa mu dongosolo desalination, choncho nthawi zambiri amabweretsedwa mu boiler kudzera madzi chakudya, amene amachepetsa pH mtengo wa boiler. madzi. Nthawi zina zinthu za organic zitha kubweretsedwanso mu nthunzi ndi madzi oundana, zomwe zingachepetse pH ndikuyambitsa dzimbiri. Zomwe zili m'madzi ozungulira m'madzi ozungulira zidzalimbikitsa kuberekana kwa tizilombo toyambitsa matenda. Chifukwa chake, kaya ndi desalination, madzi owiritsa kapena madzi ozungulira, kutsika kwa COD, kumakhala bwinoko, koma palibe cholozera chogwirizana. Pamene COD (njira ya KMnO4)> 5mg/L m'madzi ozungulira ozizirira, madziwo ayamba kunyonyotsoka.
Kufunika kwa okosijeni wa Chemical (COD) ndi chizindikiro choyezera kuchuluka kwa madzi omwe ali ndi zinthu zambiri zamoyo, komanso ndi chimodzi mwazizindikiro zofunika pakuyezera kuchuluka kwa kuipitsidwa kwa madzi. Ndi chitukuko cha mafakitale ndi kuwonjezeka kwa chiwerengero cha anthu, mabwalo amadzi akukhala oipitsidwa kwambiri, ndipo chitukuko cha COD kuzindikira chawonjezeka pang'onopang'ono.
Chiyambi cha kuzindikira kwa COD chikhoza kuyambika m'zaka za m'ma 1850, pamene mavuto owononga madzi adakopa chidwi cha anthu. Poyamba, COD inkagwiritsidwa ntchito ngati chizindikiro cha zakumwa za acidic kuyesa kuchuluka kwa zinthu zamoyo mu zakumwa. Komabe, popeza kuti njira yoyezera yokwanira inali isanakhazikitsidwe panthawiyo, panali cholakwika chachikulu pazotsatira za COD.
Kumayambiriro kwa zaka za zana la 20, ndikupita patsogolo kwa njira zamakono zowunikira mankhwala, njira yodziwira COD idasinthidwa pang'onopang'ono. Mu 1918, katswiri wa zamankhwala wa ku Germany Hasse analongosola COD monga kuchuluka kwa zinthu zamoyo zomwe zimadyedwa ndi okosijeni mu njira ya acidic. Pambuyo pake, adapereka njira yatsopano yodziwira COD, yomwe ndi kugwiritsa ntchito njira yolumikizira kwambiri ya chromium dioxide ngati oxidant. Njira imeneyi akhoza bwino oxidize organic zinthu mu mpweya woipa ndi madzi, ndi kuyeza kumwa ma okosijeni mu njira pamaso ndi pambuyo makutidwe ndi okosijeni kudziwa COD mtengo.
Komabe, zofooka za njirayi zawonekera pang'onopang'ono. Choyamba, kukonzekera ndi kugwiritsa ntchito ma reagents ndizovuta kwambiri, zomwe zimawonjezera zovuta komanso nthawi yambiri yoyesera. Chachiwiri, mayankho a chromium dioxide okhala ndi kuchuluka kwachulukidwe amakhala owopsa ku chilengedwe ndipo sakuyenera kugwiritsa ntchito bwino. Chifukwa chake, kafukufuku wotsatira pang'onopang'ono adafunafuna njira yosavuta komanso yolondola yodziwira COD.
M'zaka za m'ma 1950, katswiri wa zamankhwala wa ku Dutch Friis anatulukira njira yatsopano yodziwira COD, yomwe imagwiritsa ntchito sulfuric acid yowonjezera kwambiri monga oxidant. Njirayi ndiyosavuta kugwiritsa ntchito ndipo imakhala yolondola kwambiri, yomwe imathandizira kwambiri kuzindikira kwa COD. Komabe, kugwiritsa ntchito sulfuric acid kumakhalanso ndi zoopsa zina zachitetezo, kotero ndikofunikirabe kusamala za chitetezo cha ntchito.
Pambuyo pake, ndikukula kwachangu kwaukadaulo wa zida, njira yodziwira za COD pang'onopang'ono yakwaniritsa zodziwikiratu ndi luntha. M'zaka za m'ma 1970, chowunikira choyamba cha COD chodziwikiratu chinawonekera, chomwe chimatha kuzindikira kukonza ndi kuzindikira kwa zitsanzo za madzi. Chida ichi sichimangowonjezera kulondola komanso kukhazikika kwa kutsimikiza kwa COD, komanso kumathandizira kwambiri ntchito yabwino.
Ndi kupititsa patsogolo kuzindikira kwa chilengedwe komanso kuwongolera zofunikira pakuwongolera, njira yodziwira COD ikukonzedwanso mosalekeza. M'zaka zaposachedwa, chitukuko chaukadaulo wazithunzi, njira zama electrochemical ndi ukadaulo wa biosensor walimbikitsa luso laukadaulo la COD kuzindikira. Mwachitsanzo, ukadaulo wazithunzi ukhoza kudziwa zomwe zili mu COD mu zitsanzo zamadzi posintha ma siginecha amtundu wazithunzi, ndi nthawi yachidule yozindikira komanso kugwira ntchito kosavuta. Njira ya electrochemical imagwiritsa ntchito masensa a electrochemical kuyeza ma COD, omwe ali ndi ubwino wokhudzika kwambiri, kuyankha mofulumira komanso osafunikira ma reagents. Ukadaulo wa Biosensor umagwiritsa ntchito zida zamoyo kuti zizindikire zinthu zamoyo, zomwe zimawongolera kulondola komanso kutsimikizika kwa COD.
Njira zodziwira za COD zakhala ndi njira yachitukuko kuyambira kusanthula kwamankhwala achikale kupita ku zida zamakono, ukadaulo wazithunzi, njira za electrochemical ndi ukadaulo wa biosensor m'zaka makumi angapo zapitazi. Ndi kupita patsogolo kwa sayansi ndi ukadaulo komanso kuchuluka kwa kufunikira, ukadaulo wozindikira za COD ukukulitsidwabe ndikupangidwanso. M'tsogolomu, zitha kudziwikiratu kuti anthu akamaganizira kwambiri za kuwononga chilengedwe, ukadaulo wozindikira za COD udzakula kwambiri ndikukhala njira yodziwika bwino, yolondola komanso yodalirika yodziwira madzi.
Pakalipano, ma laboratories amagwiritsa ntchito njira ziwiri zotsatirazi kuti azindikire COD.
1. Njira yodziwira COD
Njira yokhazikika ya potaziyamu dichromate, yomwe imadziwikanso kuti njira ya reflux (National Standard of the People's Republic of China)
(I) Mfundo
Onjezani kuchuluka kwa potaziyamu dichromate ndi chothandizira siliva sulphate ku madzi chitsanzo, kutentha ndi reflux kwa nthawi inayake mu sing'anga wamphamvu acidic, mbali ya potaziyamu dichromate yafupika ndi oxidizable zinthu mu chitsanzo madzi, ndi otsala. Potaziyamu dichromate ndi titrated ndi ammonium ferrous sulfate. Mtengo wa COD umawerengedwa kutengera kuchuluka kwa potassium dichromate yomwe yadyedwa.
Popeza mulingo uwu udapangidwa mu 1989, pali zovuta zambiri pouyeza ndi mulingo wapano:
1. Zimatenga nthawi yochuluka, ndipo chitsanzo chilichonse chiyenera kusinthidwa kwa maola awiri;
2. Zida za reflux zimakhala ndi malo akuluakulu, zomwe zimapangitsa kutsimikiza kwa batch kukhala kovuta;
3. Mtengo wowunikira ndi wokwera, makamaka wa sulphate ya siliva;
4. Panthawi yotsimikiza, kutayika kwa madzi a reflux ndikodabwitsa;
5. Poizoni mercury mchere sachedwa kuipitsa yachiwiri;
6. Kuchuluka kwa ma reagents omwe amagwiritsidwa ntchito ndi aakulu, ndipo mtengo wazinthu zogwiritsira ntchito ndi wapamwamba;
7. Njira yoyeserayi ndi yovuta komanso yosayenerera kukwezedwa.
(II) Zida
1. 250mL zonse galasi reflux chipangizo
2. Chida chotenthetsera (ng'anjo yamagetsi)
3. 25mL kapena 50mL asidi burette, conical botolo, pipette, volumetric botolo, etc.
(III) Reagents
1. Potaziyamu dichromate solution (c1/6K2Cr2O7=0.2500mol/L)
2. Ferrocyanate chizindikiro njira
3. Ammonium ferrous sulfate standard solution [c(NH4)2Fe(SO4)2·6H2O≈0.1mol/L] (samalitsa musanagwiritse ntchito)
4. Sulfuric acid-silver sulphate solution
Potaziyamu dichromate muyezo njira
(IV) Njira zotsimikizira
Ammonium ferrous sulfate calibration: Pipette yolondola 10.00mL ya potassium dichromate solution mu 500mL conical botolo, chepetsani pafupifupi 110mL ndi madzi, pang'onopang'ono onjezerani 30mL ya concentrated sulfuric acid, ndipo gwedezani bwino. Mukaziziritsa, onjezerani madontho atatu a ferrocyanate indicator solution (pafupifupi 0.15mL) ndi titrate ndi ammonium ferrous sulfate solution. Pamapeto pake ndi pamene mtundu wa yankho umasintha kuchokera kuchikasu kupita ku buluu-wobiriwira kupita ku bulauni wofiira.
(V) Kutsimikiza
Tengani 20mL yachitsanzo cha madzi (ngati kuli kofunikira, tengani pang'ono ndikuwonjezera madzi ku 20 kapena kusungunula musanamwe), onjezerani 10mL wa potassium dichromate, pulagi mu chipangizo cha reflux, ndiyeno onjezerani 30mL wa sulfuric acid ndi silver sulfate, kutentha ndi reflux kwa 2h. . Mukaziziritsa, sambani khoma la condenser chubu ndi 90.00mL yamadzi ndikuchotsa botolo la conical. Njirayi ikazirala kachiwiri, onjezerani madontho atatu a ferrous acid indicator solution ndi titrate ndi ammonium ferrous sulfate standard solution. Mtundu wa yankho umasintha kuchokera ku chikasu kupita ku buluu-wobiriwira mpaka wofiira wofiira, womwe ndi mapeto ake. Lembani kuchuluka kwa ammonium ferrous sulfate standard solution. Poyezera chitsanzo cha madzi, tengani 20.00mL wa madzi odzolanso ndikuyesa opanda kanthu molingana ndi masitepe omwewo. Lembani kuchuluka kwa ammonium ferrous sulfate muyeso wogwiritsidwa ntchito mu titration yopanda kanthu.
Potaziyamu dichromate muyezo njira
(VI) Kuwerengera
CODCr(O2, mg/L)=[8×1000(V0-V1)·C]/V
(VII) Kusamala
1. Kuchuluka kwa ayoni wa kloridi wopangidwa ndi 0.4g mercuric sulfate kumatha kufika 40mg. Ngati chitsanzo cha madzi cha 20.00mL chitengedwa, kuchuluka kwa ayoni wa chloride wa 2000mg/L kumatha kupangidwa. Ngati ma ayoni a kloridi ali otsika, mercuric sulphate yocheperako imatha kuwonjezeredwa kuti musunge mercuric sulfate: ayoni a kloride = 10:1 (W/W). Ngati pang'ono mercuric kolorayidi precipitates, izo sizimakhudza kutsimikiza.
2. Mtundu wa COD womwe umatsimikiziridwa ndi njirayi ndi 50-500mg/L. Pazitsanzo za madzi zokhala ndi oxygen yofunikira yochepera 50mg/L, 0.0250mol/L potaziyamu dichromate solution iyenera kugwiritsidwa ntchito m'malo mwake. 0.01mol/L ammonium ferrous sulfate muyezo yankho ayenera kugwiritsidwa ntchito kumbuyo titration. Kwa zitsanzo za madzi okhala ndi COD kuposa 500mg/L, tsitsani musanadziwe.
3. Pambuyo pa chitsanzo cha madzi kutenthedwa ndi kusinthidwa, potassium dichromate yotsala mu yankho iyenera kukhala 1/5-4/5 ya kuchuluka kwake.
4. Mukamagwiritsa ntchito potassium hydrogen phthalate standard solution kuti muwone luso ndi luso la ntchito ya reagent, popeza CODCr yachidziwitso cha galamu iliyonse ya potassium hydrogen phthalate ndi 1.176g, 0.4251g ya potassium hydrogen phthalate (HOOCC6H4COOK) imasungunuka m'madzi osungunuka, amasamutsidwa ku botolo la voliyumu ya 1000mL, ndikuchepetsedwa mpaka chizindikirocho ndi madzi odzola kuti apange njira yokhazikika ya 500mg/L CODcr. Konzekerani mwatsopano mukagwiritsidwa ntchito.
5. Zotsatira za CODCr ziyenera kukhala ndi manambala anayi ofunikira.
6. Pakuyesa kulikonse, yankho la ammonium ferrous sulfate titration liyenera kusinthidwa, ndipo kusintha kwa ndende kuyenera kuperekedwa chisamaliro chapadera pamene kutentha kwa chipinda kuli kwakukulu. (Mungathenso kuwonjezera 10.0ml ya potaziyamu dichromate yankho lokhazikika ku chopanda kanthu pambuyo pa titration ndi titrate ndi ammonium ferrous sulfate mpaka kumapeto.)
7. Chitsanzo cha madzi chiyenera kusungidwa mwatsopano ndikuyezedwa mwamsanga.
Ubwino:
Kulondola kwakukulu: Reflux titration ndi njira yachikale yodziwira COD. Pambuyo pa nthawi yayitali ya chitukuko ndi kutsimikizira, kulondola kwake kwadziwika kwambiri. Ikhoza kuwonetsa bwino zomwe zili m'madzi.
Kugwiritsa ntchito kwambiri: Njirayi ndi yoyenera pamitundu yosiyanasiyana yamadzi, kuphatikiza madzi otayira kwambiri komanso otsika kwambiri.
Mafotokozedwe a ntchito: Pali miyezo ndi njira zogwirira ntchito, zomwe ndizosavuta kuti ogwiritsa ntchito azidziwa bwino ndikuzigwiritsa ntchito.
Zoyipa:
Kutenga nthawi: Reflux titration nthawi zambiri imatenga maola angapo kuti amalize kutsimikiza kwa zitsanzo, zomwe mwachiwonekere sizikugwirizana ndi zomwe zotsatira zake ziyenera kupezedwa mwachangu.
Kugwiritsa ntchito kwambiri reagent: Njirayi imafuna kugwiritsa ntchito mankhwala opangira mankhwala, omwe si okwera mtengo okha, komanso amawononga chilengedwe kumlingo winawake.
Kugwira ntchito movutikira: Wogwiritsa ntchito ayenera kukhala ndi chidziwitso chamankhwala ndi luso loyesera, apo ayi zitha kukhudza kulondola kwa zotsatira zake.
2. Rapid chimbudzi spectrophotometry
(I) Mfundo
Chitsanzocho chimawonjezeredwa ndi njira yodziwika ya potaziyamu dichromate, muzitsulo zolimba za sulfuric acid, ndi siliva sulphate monga chothandizira, ndipo pambuyo pa kutentha kwapamwamba, mtengo wa COD umatsimikiziridwa ndi zipangizo za photometric. Popeza njira imeneyi ndi yochepa kutsimikiza nthawi, yaing'ono yachiwiri kuipitsa, yaing'ono reagent voliyumu ndi mtengo wotsika, ma laboratories ambiri panopa ntchito njira. Komabe, njirayi ili ndi mtengo wokwera wa zida komanso mtengo wotsika mtengo, womwe ndi woyenera kugwiritsa ntchito nthawi yayitali mayunitsi a COD.
(II) Zida
Zida zakunja zidapangidwa kale, koma mtengo wake ndi wapamwamba kwambiri, ndipo nthawi yotsimikiza ndi yayitali. Mtengo wa reagent nthawi zambiri umakhala wosatheka kwa ogwiritsa ntchito, ndipo kulondola kwake sikokwera kwambiri, chifukwa miyezo yowunikira zida zakunja ndi yosiyana ndi ya dziko langa, makamaka chifukwa mlingo wa mankhwala amadzi ndi kayendetsedwe ka kayendetsedwe ka mayiko akunja ndi osiyana ndi anga. dziko; mofulumira chimbudzi spectrophotometry njira makamaka zochokera njira wamba zida zapakhomo. Kutsimikiza kofulumira kwa njira ya COD ndiye mulingo wamapangidwe a njirayi. Linapangidwa koyambirira kwa zaka za m'ma 1980. Pambuyo pazaka zopitilira 30 zogwiritsidwa ntchito, zakhala muyezo wamakampani oteteza zachilengedwe. Chida chapakhomo cha 5B chakhala chikugwiritsidwa ntchito kwambiri pofufuza zasayansi komanso kuwunika kovomerezeka. Zida zapakhomo zakhala zikugwiritsidwa ntchito kwambiri chifukwa cha ubwino wamtengo wapatali komanso ntchito yotsatsa panthawi yake.
(III) Njira zotsimikizira
Tengani chitsanzo cha 2.5ml—–add reagent—–digest for 10 minutes—–oziziritsa kwa mphindi 2—–kutsanulira mu mbale ya colorimetric—–zida zowonetsera zimasonyeza mwachindunji COD ndende ya chitsanzo.
(IV) Kusamala
1. Zitsanzo za madzi ochuluka a chlorine ayenera kugwiritsa ntchito reagent ya chlorine.
2. Madzi otayira amakhala pafupifupi 10ml, koma amakhala acidic kwambiri ndipo ayenera kusonkhanitsidwa ndikukonzedwa.
3. Onetsetsani kuti podutsa kuwala kwa cuvette ndi koyera.
Ubwino:
Kuthamanga Kwambiri: Njira yofulumira nthawi zambiri imangotenga mphindi zochepa mpaka mphindi khumi kuti mutsirize kutsimikiza kwa chitsanzo, chomwe chiri choyenera kwambiri pazochitika zomwe zotsatira ziyenera kupezedwa mwamsanga.
Kuchepetsa kugwiritsa ntchito reagent: Poyerekeza ndi njira ya reflux titration, njira yofulumira imagwiritsa ntchito ma reagents ochepa amankhwala, imakhala ndi ndalama zotsika, ndipo imakhala ndi mphamvu zochepa pa chilengedwe.
Kuchita kosavuta: Masitepe opangira njira yofulumira ndi yosavuta, ndipo wogwiritsa ntchito sayenera kukhala ndi chidziwitso chambiri chamankhwala ndi luso loyesera.
Zoyipa:
Kulondola pang'ono: Popeza kuti njira yofulumira nthawi zambiri imagwiritsa ntchito njira zosavuta zopangira mankhwala ndi njira zoyezera, kulondola kwake kungakhale kotsika pang'ono kuposa njira ya reflux titration.
Kuchulukirachulukira kwakugwiritsa ntchito: Njira yofulumira ndiyoyenera kutsimikizira madzi otayira omwe ali otsika kwambiri. Kwa madzi otayira kwambiri, zotsatira zake zitha kukhudzidwa kwambiri.
Kukhudzidwa ndi zinthu zosokoneza: Njira yofulumira ikhoza kutulutsa zolakwika zazikulu muzochitika zina zapadera, monga pamene pali zinthu zina zosokoneza mumtsuko wa madzi.
Mwachidule, njira ya reflux titration ndi njira yofulumira iliyonse ili ndi zabwino ndi zovuta zake. Ndi njira iti yomwe mungasankhire zimadalira momwe mungagwiritsire ntchito komanso zosowa. Pamene kulondola kwakukulu ndi kugwiritsiridwa ntchito kwakukulu kumafunika, reflux titration ikhoza kusankhidwa; pamene zotsatira zofulumira zimafunika kapena chiwerengero chachikulu cha zitsanzo za madzi chikukonzedwa, njira yofulumira ndi yabwino kusankha.
Lianhua, monga wopanga zida zoyesera zamadzi kwa zaka 42, apanga mphindi 20.COD mofulumira chimbudzi spectrophotometrynjira. Pambuyo pa mafananidwe ambiri oyesera, atha kukwaniritsa zolakwika zosakwana 5%, ndipo ali ndi ubwino wa ntchito yosavuta, zotsatira zofulumira, zotsika mtengo komanso nthawi yochepa.
Nthawi yotumiza: Jun-07-2024
